I need to purchase one but I'm confused about the sizing. Do you just go by the largest measurement across your chest and ignore cup size? I'm just afraid of ordering something that may not be snug enough for my ribcage.

Or if anyone knows of a reptuable swimsuit website for the "well endowed" that would be swell.

I think that most swimwear companies ignore cup size, unless they specifically say there is a cup size.

Here is a company that does sell bathing suits by cup size and ribcage size. They have all sorts of sizes for the well-endowed who also have small ribcages. (They also have some great stappy tops that seem to have been designed by an engineer!) Look at Bravissimo swimwear

Be sure to click on the sale link. There are more styles there.

It is a UK company. But I have had very good experiences ordering from them.

"A musician must make music, an artist must paint, a poet must write, if he is to be ultimately at peace with himself." --- Abraham Maslow

I was able to wear my "tankini" for the first few months of my pregnancy (not as revealing as a bikini, but not as binding as a full suit) If you don't want to get a maternity suit, try on larger tankini styles.